The production of rubber for a vehicle tire includes a plurality of successive mixing steps. For example, patent GB423,637 discloses a means for maintaining a predetermined temperature of rubber during mixing on a roller tool. This means operates by expansion and contraction of an element that responds to the change in the rubber temperature and sends water to the open mill. An initial mixture of elastomeric materials with a carbon black filler and/or silica is often carried out inside a mixer, where the temperature of the mixture rises, for example up to values of between 150° C. to 200° C. An automated external mixer (also called “roll mixer” or “roller tool”) in which this mixture is then transferred works the mixture, causing it to flow between two rolls so as to convert it into a continuous sheet. Vulcanization products (including, without limitation, sulfur) may be added to the mixture later in the mixing cycle to obtain the final mixture for commercial use.
During the mixing process, repeated rolling results in plasticization of the mixture and causes the temperature to rise accordingly. The mixture is cooled to prevent premature partial vulcanization and/or degradation of insoluble additives. To perform cooling, some methods include cooling fans or integrated cooling systems (e.g., fluid circulating within the cylinders). Other methods employ spray and aspiration equipment that add water to the mixture being worked.
The properties of the mixture, however, are very sensitive to the proportions of its constituent ingredients. Added water can compromise the quality of the finished tire. Vaporization offers an effective solution to cool the mixture and can be used with temperature control during mixing so that the beneficial properties of the tires are preserved.